docs(configure-redis-using-configmap): update for clarity (#25712)

* docs(configure-redis-using-configmap): update for clarity

Signed-off-by: Jai Govindani <[email protected]>

* fix(configure-redis-using-configmap): incorrect volumeMount index

Signed-off-by: Jai Govindani <[email protected]>

* fix(configure-redis-using-configmap): show Pod status as Running, separate commands from output

Signed-off-by: Jai Govindani <[email protected]>

* fix(configure-redis-using-configmap): typo

Signed-off-by: Jai Govindani <[email protected]>

* fix(configure-redis-using-configmap): configmap name

Signed-off-by: Jai Govindani <[email protected]>

Author: jai

content/en/docs/tutorials/configuration/configure-redis-using-configmap.md

@@ -15,10 +15,8 @@ This page provides a real world example of how to configure Redis using a Config
 ## {{% heading "objectives" %}}
 
 
-* Create a `kustomization.yaml` file containing:
-  * a ConfigMap generator
-  * a Pod resource config using the ConfigMap
-* Apply the directory by running `kubectl apply -k ./`
+* Create a ConfigMap with Redis configuration values
+* Create a Redis Pod that mounts and uses the created ConfigMap
 * Verify that the configuration was correctly applied.
 
 
@@ -38,82 +36,218 @@ This page provides a real world example of how to configure Redis using a Config
 
 ## Real World Example: Configuring Redis using a ConfigMap
 
-You can follow the steps below to configure a Redis cache using data stored in a ConfigMap.
+Follow the steps below to configure a Redis cache using data stored in a ConfigMap.
 
-First create a `kustomization.yaml` containing a ConfigMap from the `redis-config` file:
-
-{{< codenew file="pods/config/redis-config" >}}
+First create a ConfigMap with an empty configuration block:
 
 ```shell
-curl -OL https://k8s.io/examples/pods/config/redis-config
-
-cat <<EOF >./kustomization.yaml
-configMapGenerator:
-- name: example-redis-config
-  files:
-  - redis-config
+cat <<EOF >./example-redis-config.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: example-redis-config
+data:
+  redis-config: ""
 EOF
 ```
 
-Add the pod resource config to the `kustomization.yaml`:
+Apply the ConfigMap created above, along with a Redis pod manifest:
+
+```shell
+kubectl apply -f example-redis-config.yaml
+kubectl apply -f https://raw.githubusercontent.com/kubernetes/website/master/content/en/examples/pods/config/redis-pod.yaml
+```
+
+Examine the contents of the Redis pod manifest and note the following:
+
+* A volume named `config` is created by `spec.volumes[1]`
+* The `key` and `path` under `spec.volumes[1].items[0]` exposes the `redis-config` key from the 
+  `example-redis-config` ConfigMap as a file named `redis.conf` on the `config` volume.
+* The `config` volume is then mounted at `/redis-master` by `spec.containers[0].volumeMounts[1]`.
+
+This has the net effect of exposing the data in `data.redis-config` from the `example-redis-config`
+ConfigMap above as `/redis-master/redis.conf` inside the Pod.
 
 {{< codenew file="pods/config/redis-pod.yaml" >}}
 
+Examine the created objects:
+
 ```shell
-curl -OL https://raw.githubusercontent.com/kubernetes/website/master/content/en/examples/pods/config/redis-pod.yaml
+kubectl get pod/redis configmap/example-redis-config 
+```
 
-cat <<EOF >>./kustomization.yaml
-resources:
-- redis-pod.yaml
-EOF
+You should see the following output:
+
+```shell
+NAME        READY   STATUS    RESTARTS   AGE
+pod/redis   1/1     Running   0          8s
+
+NAME                             DATA   AGE
+configmap/example-redis-config   1      14s
 ```
 
-Apply the kustomization directory to create both the ConfigMap and Pod objects:
+Recall that we left `redis-config` key in the `example-redis-config` ConfigMap blank:
 
 ```shell
-kubectl apply -k .
+kubectl describe configmap/example-redis-config
 ```
 
-Examine the created objects by
+You should see an empty `redis-config` key:
+
 ```shell
-> kubectl get -k .
-NAME                                        DATA   AGE
-configmap/example-redis-config-dgh9dg555m   1      52s
+Name:         example-redis-config
+Namespace:    default
+Labels:       <none>
+Annotations:  <none>
+
+Data
+====
+redis-config:
+```
 
-NAME        READY   STATUS    RESTARTS   AGE
-pod/redis   1/1     Running   0          52s
+Use `kubectl exec` to enter the pod and run the `redis-cli` tool to check the current configuration:
+
+```shell
+kubectl exec -it redis -- redis-cli
+```
+
+Check `maxmemory`:
+
+```shell
+127.0.0.1:6379> CONFIG GET maxmemory
+```
+
+It should show the default value of 0:
+
+```shell
+1) "maxmemory"
+2) "0"
+```
+
+Similarly, check `maxmemory-policy`:
+
+```shell
+127.0.0.1:6379> CONFIG GET maxmemory-policy
+```
+
+Which should also yield its default value of `noeviction`:
+
+```shell
+1) "maxmemory-policy"
+2) "noeviction"
+```
+
+Now let's add some configuration values to the `example-redis-config` ConfigMap:
+
+{{< codenew file="pods/config/example-redis-config.yaml" >}}
+
+Apply the updated ConfigMap:
+
+```shell
+kubectl apply -f example-redis-config.yaml
+```
+
+Confirm that the ConfigMap was updated:
+
+```shell
+kubectl describe configmap/example-redis-config
 ```
 
-In the example, the config volume is mounted at `/redis-master`.
-It uses `path` to add the `redis-config` key to a file named `redis.conf`.
-The file path for the redis config, therefore, is `/redis-master/redis.conf`.
-This is where the image will look for the config file for the redis master.
+You should see the configuration values we just added:
 
-Use `kubectl exec` to enter the pod and run the `redis-cli` tool to verify that
-the configuration was correctly applied:
+```shell
+Name:         example-redis-config
+Namespace:    default
+Labels:       <none>
+Annotations:  <none>
+
+Data
+====
+redis-config:
+----
+maxmemory 2mb
+maxmemory-policy allkeys-lru
+```
+
+Check the Redis Pod again using `redis-cli` via `kubectl exec` to see if the configuration was applied:
 
 ```shell
 kubectl exec -it redis -- redis-cli
+```
+
+Check `maxmemory`:
+
+```shell
 127.0.0.1:6379> CONFIG GET maxmemory
+```
+
+It remains at the default value of 0:
+
+```shell
 1) "maxmemory"
-2) "2097152"
+2) "0"
+```
+
+Similarly, `maxmemory-policy` remains at the `noeviction` default setting:
+
+```shell
 127.0.0.1:6379> CONFIG GET maxmemory-policy
+```
+
+Returns:
+
+```shell
 1) "maxmemory-policy"
-2) "allkeys-lru"
+2) "noeviction"
 ```
 
-Delete the created pod:
+The configuration values have not changed because the Pod needs to be restarted to grab updated
+values from associated ConfigMaps. Let's delete and recreate the Pod:
+
 ```shell
 kubectl delete pod redis
+kubectl apply -f https://raw.githubusercontent.com/kubernetes/website/master/content/en/examples/pods/config/redis-pod.yaml
 ```
 
+Now re-check the configuration values one last time:
 
+```shell
+kubectl exec -it redis -- redis-cli
+```
 
-## {{% heading "whatsnext" %}}
+Check `maxmemory`:
 
+```shell
+127.0.0.1:6379> CONFIG GET maxmemory
+```
 
-* Learn more about [ConfigMaps](/docs/tasks/configure-pod-container/configure-pod-configmap/).
+It should now return the updated value of 2097152:
 
+```shell
+1) "maxmemory"
+2) "2097152"
+```
+
+Similarly, `maxmemory-policy` has also been updated:
 
+```shell
+127.0.0.1:6379> CONFIG GET maxmemory-policy
+```
 
+It now reflects the desired value of `allkeys-lru`:
 
+```shell
+1) "maxmemory-policy"
+2) "allkeys-lru"
+```
+
+Clean up your work by deleting the created resources:
+
+```shell
+kubectl delete pod/redis configmap/example-redis-config
+```
+
+## {{% heading "whatsnext" %}}
+
+
+* Learn more about [ConfigMaps](/docs/tasks/configure-pod-container/configure-pod-configmap/).

content/en/examples/pods/config/example-redis-config.yaml

@@ -0,0 +1,8 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: example-redis-config
+data:
+  redis-config: |
+    maxmemory 2mb
+    maxmemory-policy allkeys-lru